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PubMed2004

Nutritional condition and serum biochemistry for free-living Swainson's Hawks wintering in central Argentina.

We assessed the nutritional condition and established reference values for serum chemistry parameters in a long distance migrant bird of prey, the Swainson's Hawk (Buteo swainsoni), wintering in central Argentina. We analyzed serum concentration of urea, uric acid, cholesterol, and triglycerides and assessed age and sex related differences in these parameters. A body condition index was obtained from the resultant residuals of the regression of body mass and a morphometric measure. No statistical differences were observed among sex and age groups for urea, uric acid and triglyceride serum concentration. However, cholesterol concentration differed among male and female hawks, which could be related to the gain of body mass in wintering grounds at differential rates. The mean values of the four parameters were in the range of those recorded in the Common Buzzard (Buteo buteo), indicating good nutritional condition of the population we studied. Forearm length was the morphometric variable that better correlated with body mass. The resultant body condition index was only correlated with triglyceride concentration, suggesting that this index could be valuable in future work dealing with the assessment of body fat storage in wintering and breeding hawks, as well as in stopover points on the migratory route.

Animal Migration↗
PubMed1991

Effect of sublethal lead exposure on gastric motility of red-tailed hawks.

In order to determine the effects of low level lead exposure on gastric motility in raptors, strain gage transducers were surgically implanted on the serosal surface of the muscular stomach of three red-tailed hawks. The frequency and amplitude of gastric contractions during ingestion and early digestion were monitored for 1 week under control conditions and for 3 weeks while the birds were fed 0.82 or 1.64 mg lead (as lead acetate) per kg body weight each day. Exposure to these doses did not appreciably affect either the frequency or amplitude of gastric contractions in these birds. This low level lead exposure also had no consistent effect on the regular egestion of pellets of undigested material by hawks. Daily exposure to doses up to 6.55 mg lead/kg body weight did not affect the frequency or timing of pellet egestion, and exposure to 1.64 mg lead/kg did not affect the gastric contractions associated with pellet egestion. Although gastrointestinal dysfunction is often associated with clinical cases of acute lead toxicity, chronic exposure to these low levels of lead acetate did not significantly alter gastric motility in red-tailed hawks.

Animals↗
PubMed2003

Echolocation range and wingbeat period match in aerial-hawking bats.

Aerial-hawking bats searching the sky for prey face the problem that flight and echolocation exert independent and possibly conflicting influences on call intervals. These bats can only exploit their full echolocation range unambiguously if they emit their next call when all echoes from the preceding call would have arrived. However, not every call interval is equally available. The need to reduce the high energetic costs of echolocation forces aerial-hawking bats to couple call emission to their wingbeat. We compared the wingbeat periods of 11 aerial-hawking bat species with the delays of the last-expected echoes. Acoustic flight-path tracking was employed to measure the source levels (SLs) of echolocation calls in the field. SLs were very high, extending the known range to 133 dB peak equivalent sound pressure level. We calculated the maximum detection distances for insects, larger flying objects and background targets. Wingbeat periods were derived from call intervals. Small and medium-sized bats in fact matched their maximum detection range for insects and larger flying targets to their wingbeat period. The tendency to skip calls correlated with the species' detection range for background targets. We argue that a species' call frequency is at such a pitch that the resulting detection range matches their wingbeat period.

Animals↗
PubMed2005

Hawking radiation in sonic black holes.

I present a microscopic description of Hawking radiation in sonic black holes. A one-dimensional Fermi-degenerate liquid squeezed by a smooth barrier forms a transonic flow, a sonic analog of a black hole. The quantum treatment of the noninteracting case establishes a close relationship between sonic Hawking radiation and quantum tunneling through the barrier. Quasiparticle excitations appear at the barrier and are then radiated with a thermal distribution in exact agreement with Hawking's formula. The signature of the radiation can be found in the dynamic structure factor, which can be measured in a scattering experiment. The possibility for experimental verification of this new transport phenomenon for ultracold atoms is discussed.

Journal Article↗
PubMedDate not supplied

Changes in body mass index in 11-12-year-old children in Hawkes Bay, New Zealand (1989-2000).

OBJECTIVE: To describe and compare the body mass index (BMI; weight/height2) profile of 11-12-year-old children in Hawkes Bay, New Zealand in 1989 and 2000. To subsequently determine the prevalence of overweight and obesity at the two time points using international definitions. METHODOLOGY: As part of asthma prevalence studies in Hawkes Bay data on height, weight and ethnicity were collected from 871 school children in 1989, and 894 children in 2000 who reached 12 years of age during the year of testing. RESULTS: In the total study population the geometric mean BMI increased from 18.1 kg/m2 (95% CI 17.9; 18.3) in 1989 to 19.8 kg/m2 (95% CI 19.6; 20.0) in 2000, a relative increase of 9.2% (95% CI 7.6; 10.9), P < 0.001. Significant relative increases were found for males (9.0%: 95% CI 6.8; 11.3), females (9.3%: 95% CI 6.8; 11.8), Maori (7.6%: 95% CI 4.3; 11.1), European (9.1%: 95% CI 7.3; 11.0) and Pacific Island children (11.0%: 95% CI 2.2; 20.5). In 2000 20.9% of Hawkes Bay children were classified as overweight and 9.1% as obese. The risk of being overweight in 2000 was 2.2 times greater than the risk in 1989, and the risk of being obese was 3.8 times greater, with these problems more pronounced among Maori (overweight 24.7%, obese 15.3%) and Pacific Island (overweight 35.0%, obese 15.0%) than European (overweight: 18.2%, obese 5.7%) children. However, the risk of being overweight (RR = 3.0, 95% CI 2.2-4.0) or obese (RR = 8.3, 95% CI 3.0-23.3) in 2000 compared to 1989 was greater among European children. CONCLUSION: Higher percentages of Maori and Pacific Island children are overweight or obese compared to European, but in all ethnic groups there has been a statistically significant increase in mean BMI over an 11-year period. This increase reflects the trend observed in other developed countries and underlines childhood obesity as a major health problem in New Zealand.

Body Mass Index↗
PubMedDate not supplied

Hawk calls elicit alarm and defensive reactions in captive Geoffroy's marmosets (Callithrix geoffroyi).

Most descriptions of callitrichid antipredator behavior have come from observations of visual encounters with predators, but there is also anecdotal evidence suggesting that callitrichids may use auditory cues associated with raptors for the early detection of potential danger. In the present study, Geoffroy's marmosets consistently reacted to the tape-recorded calls of a red-tailed hawk (Buteo jamaicensis) with high-intensity antipredator behaviors. Compared to the taped calls of a raven (Corvus corax) and the taped sound of a power drill, the hawk calls elicited more startle reactions, more alarm calls, longer freeze times, increased use of safe areas of their enclosure and greater disruption in ongoing behavior. Once in a relatively safe location in the enclosure, the marmosets visually monitored the site of origin of the calls for 10 min and minimized locomotion for 30 min, but resumed baseline levels of other activities that had been disrupted by the hawk calls. Marmosets may use the auditory cues associated with predators for early detection, and subsequent avoidance, of a potential predator in the vicinity.

Animals↗
PubMed2000

Gliding flight: drag and torque of a hawk and a falcon with straight and turned heads, and a lower value for the parasite drag coefficient.

Raptors - falcons, hawks and eagles in this study - such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 degrees to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s(-)(1). With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct. The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor's higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals. In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (C(D,par)) of 0.18 previously used for calculating the gliding performance of a peregrine. The accuracy with which drag coefficients measured on wingless bird bodies in a wind tunnel represent the C(D,par) of a living bird is unknown. Another method for determining C(D,par) selects values that improve the fit between speeds predicted by mathematical models and those observed in living birds. This method yields lower values for C(D,par) (0.05-0.07) than wind tunnel measurements, and the present study suggests a value of 0.1 for raptors as a compromise.

Air Movements↗
PubMed1975

Fatal pox infection in a rough-legged hawk.

Natural pox infection occurred in a free-living rough-legged hawk (Buteo lagopus) in northeastern North Dakota. Gross, histological and electron microscopic findings were typical of pox infection, and characteristic lesions developed in red-tailed hawks (Buteo jamaicensis) but not in great horned owls (Bubo virginianus) following inoculation with case material. Death of the rough-legged hawk was attributed to starvation rsulting from inability to capture prey and to blood loss from foot lesions.

Animals↗
PubMed1992

The red-tailed hawk, Buteo jamaicensis, a native definitive host of Frenkelia microti (Apicomplexa) in North America.

Oral inoculation of prairie voles, Microtus ochrogaster, with coccidian sporocysts isolated from the feces of a red-tailed hawk, Buteo jamaicensis, in Kansas, USA, resulted in formation of Frenkelia microti (Apicomplexa: Sarcocystidae) tissue cysts in the brains of the voles. Five additional isolates of morphologically similar sporocysts collected from red-tailed hawks or other Buteo spp. in Kansas failed to result in detectable infections in rodents. These results are the first to verify that red-tailed hawks are natural definitive host in North America for F. microti.

Animals↗
PubMed1999

A comprehensive noise survey of the S-70A-9 Black Hawk helicopter.

PURPOSE: This paper reports the results of a comprehensive noise survey of the Sikorsky S-70A-9 Black Hawk helicopter environment and provides an assessment of the hearing protection devices worn by Australian Army personnel exposed to that environment. METHODS AND RESULTS: At-ear noise levels were measured at 4 positions in the cabin of the Black Hawk under various flight conditions and at 13 positions outside the Black Hawk under various ground running conditions using the Head Acoustic Measurement System (Head, GmbH). The attenuation properties of the hearing protection devices (HPDs) normally worn by aircrew and maintenance crews (the ALPHA helmet and the Roanwell MX-2507 Communications headset) were also assessed. At-ear sound pressure levels that would be experienced by personnel wearing their normal HPDs were determined at the positions they would normally occupy in and around the aircraft. CONCLUSION: Results indicate that HPDs do not provide adequate hearing protection to meet current hearing conservation regulations which allow a permissible noise exposure of 85 dB(A) for an 8-h day.

Acoustics↗
PubMed1984

Use of whole blood lymphocyte stimulation test for immunocompetency studies in bald eagles, red-tailed hawks, and great horned owls.

Mitogen-induced whole blood lymphocyte stimulation tests for immunocompetency studies in bald eagles (Haliaeetus leucocephalus), red-tailed hawks (Buteo jamaicensis), and great horned owls (Bubo virginianus) were developed. Combinations of incubation times, blood dilutions, concentrations of [3H]thymidine and [125I]2-deoxyuridine, antibiotics, phytohemagglutinin-P, and concanavalin A were tested for their effects on the stimulation index (SI). An antibiotic combination of gentamicin plus amphotericin B yielded low SI with lymphocytes from bald eagles, but not with lymphocytes from great horned owls or red-tailed hawks. Penicillin plus streptomycin caused no such depression of SI. Lymphocytes from all 3 species yielded maximum responses with a 48-hour prelabel and 12- to- 16 hour postlabel incubation period at 41 C and 1:20 blood dilution. Optimal mitogen concentrations for lymphocytes from bald eagles, red-tailed hawks, and great horned owls were 25 micrograms, 10 micrograms, and 10 micrograms of phytohemagglutinin-P/well, respectively, and 2.5 micrograms, 10 micrograms, and 10 micrograms of concanavalin A/well, respectively. Differences in SI were not seen between the 2 radioactive labels. The optimal concentration of the [3H]thymidine label ranged from 0.06 to 0.125 microCi/well.

Amphotericin B↗
PubMed2005

Effects of Holocene climate change on the historical demography of migrating sharp-shinned hawks (Accipiter striatus velox) in North America.

DNA sequences of the mitochondrial control region were analysed from 298 individual sharp-shinned hawks (Accipiter striatus velox) sampled at 12 different migration study sites across North America. The control region proved to be an appropriate genetic marker for identification of continental-scale population genetic structure and for determining the historical demography of population units. These data suggest that sharp-shinned hawks sampled at migration sites in North America are divided into distinct eastern and western groups. The eastern group appears to have recently expanded in response to the retreat of glacial ice at the end of the last glacial maximum. The western group appears to have been strongly effected by the Holocene Hypsithermal dry period, with molecular evidence indicating the most recent expansion following this mid-Holocene climatic event 7000-5000 years before present.

Animals↗
PubMed2006

Polyphyly of the hawk genera Leucopternis and Buteogallus (Aves, Accipitridae): multiple habitat shifts during the Neotropical buteonine diversification.

BACKGROUND: The family Accipitridae (hawks, eagles and Old World vultures) represents a large radiation of predatory birds with an almost global distribution, although most species of this family occur in the Neotropics. Despite great morphological and ecological diversity, the evolutionary relationships in the family have been poorly explored at all taxonomic levels. Using sequences from four mitochondrial genes (12S, ATP8, ATP6, and ND6), we reconstructed the phylogeny of the Neotropical forest hawk genus Leucopternis and most of the allied genera of Neotropical buteonines. Our goals were to infer the evolutionary relationships among species of Leucopternis, estimate their relationships to other buteonine genera, evaluate the phylogenetic significance of the white and black plumage patterns common to most Leucopternis species, and assess general patterns of diversification of the group with respect to species' affiliations with Neotropical regions and habitats. RESULTS: Our molecular phylogeny for the genus Leucopternis and its allies disagrees sharply with traditional taxonomic arrangements for the group, and we present new hypotheses of relationships for a number of species. The mtDNA phylogenetic trees derived from analysis of the combined data posit a polyphyletic relationship among species of Leucopternis, Buteogallus and Buteo. Three highly supported clades containing Leucopternis species were recovered in our phylogenetic reconstructions. The first clade consisted of the sister pairs L. lacernulatus and Buteogallus meridionalis, and Buteogallus urubitinga and Harpyhaliaetus coronatus, in addition to L. schistaceus and L. plumbeus. The second clade included the sister pair Leucopternis albicollis and L. occidentalis as well as L. polionotus. The third lineage comprised the sister pair L. melanops and L. kuhli, in addition to L. semiplumbeus and Buteo buteo. According to our results, the white and black plumage patterns have evolved at least twice in the group. Furthermore, species found to the east and west of the Andes (cis-Andean and trans-Andean, respectively) are not reciprocally monophyletic, nor are forest and non-forest species. CONCLUSION: The polyphyly of Leucopternis, Buteogallus and Buteo establishes a lack of concordance of current Accipitridae taxonomy with the mtDNA phylogeny for the group, and points to the need for further phylogenetic analysis at all taxonomic levels in the family as also suggested by other recent analyses. Habitat shifts, as well as cis- and trans-Andean disjunctions, took place more than once during buteonine diversification in the Neotropical region. Overemphasis of the black and white plumage patterns has led to questionable conclusions regarding the relationships of Leucopternis species, and suggests more generally that plumage characters should be used with considerable caution in the taxonomic evaluation of the Accipitridae.

Animals↗
PubMed2004

Knemidokoptes in a Swainson's hawk, Buteo swainsoni.

A male Swainson's hawk (Buteo swainsoni) at a rehabilitation facility in Colorado was presented with severe crusting of the skin on the medial thighs and caudal ventral body. Male and female Knemidokoptes mites were found on a cellophane tape preparation of the affected area. The hawk's clinical signs resolved with treatment with ivermectin administered at 200 microg/kg, i.m., every 10 days for three treatments.

Animals↗
PubMed2005

Hailstorms as a cause of mass mortality of Swainson's hawks in their wintering grounds.

We describe a mass mortality event of wintering Swainson's hawks (SH, Buteo swainsoni) in central Argentina during November 2003. One hundred thirteen SH were found dead as a consequence of a single hailstorm. In addition, 14 hawks with severe injuries were recovered alive, but only 10 of these survived 1 wk later. Another 45 dead birds of 11 species were collected in the area. Interviews with local land-owners conducted in other areas of the SH wintering grounds provided further evidence of past hailstorm-related mortality involving SH, suggesting that such events commonly occur in the Argentine Pampas. This potential cause of mass mortality of SH wintering in agricultural areas of Argentina may be significant when added to the increased mortality associated with poisoning events during the last decade.

Animals↗
PubMed1991

Effects of chronic exposure to sublethal concentrations of lead acetate on heme synthesis and immune function in red-tailed hawks.

Red-tailed hawks were exposed to sublethal levels of lead acetate for periods of 3 or 11 weeks. Alterations in the heme biosynthetic pathway were demonstrated after the first week of exposure to 0.82 mg lead per kilogram body weight per day. Activity of erythrocyte porphobilinogen synthase (aminolevulinic acid dehydratase) was depressed significantly and did not return to normal levels until 5 weeks after the termination of lead treatments. A rapid and relatively brief increase in erythrocyte free protoporphyrin and a slower but more prolonged increase in its zinc complex were also demonstrated with exposure to this dose of lead for 3 weeks. Less substantial decreases in hematocrit and hemoglobin levels occurred but only in the longer experiment with exposure to higher lead levels. Short term, low level lead exposure did not effect immune function significantly in the hawks, as measured by antibody titers to foreign red blood cells or by the mitogenic stimulation of T-lymphocytes. Increased lead exposure produced a significant decrease in the mitogenic response but had no effect on antibody titers.

Animals↗
PubMed1998

Visual position stabilization in the hummingbird hawk moth, Macroglossum stellatarum L. I. Behavioural analysis.

Optomotor responses of freely flying hawk moths, Macroglossum stellatarum, were characterized while the animals were hovering in front of and feeding on a dummy flower. Compensatory translational and rotational movements of the hawk moth were elicited by vertical grating patterns moving horizontally, mimicking imposed rotational and translational displacements of the animal in the horizontal plane. Oscillatory translational and rotational pattern motion leads to compensatory responses that peak in the frequency range between 2 Hz and 4 Hz. The control systems mediating the translational and rotational components of the optomotor response do not seem to influence each other. The system mediating translational responses is more sensitive in the fronto-lateral part of the visual field than in the lateral part; the opposite is true for the rotational system. The sensitivity of the translational system does not change along the vertical, whereas the rotational system is much more sensitive to motion in the dorsal than in the ventral part of the visual field. These sensitivity gradients may reflect an adaptation to the specific requirements of position stabilization in front of flowers during feeding.

Animals↗
PubMedDate not supplied

A predator-prey model with predators using hawk and dove tactics.

In this work we present a predator-prey model that incorporates individual behavior of the predators. A classical Lotka-Volterra model with self-limiting prey describes the predator-prey interaction. Predator individuals can use two behavioral tactics to dispute a prey when they meet, the classical hawk and dove tactics. Each individual can use both tactics along its life. The predator behavioral change is described by means of a game dynamic model based upon the replicator equations, where the gain depends on prey density. We assume that the demographic process, predator-prey interactions, acts at a slow time scale in comparison with the evolution of the behavior of the predator population. The existence of two time scales allows studying the complete system from a reduced one, which describes the dynamics of the total predator and prey densities at the slow time scale. The aim of this work is to study the effects of individual predator behavior on the dynamics of the predator-prey system. The main conclusion that emerges from this study is the existence of a relationship between prey density and the strategy adopted by predators: aggressive behavior is connected to high prey and low predator densities, whereas a polymorphism dove-hawk is found at low prey and high predator densities.

Animals↗